Stethoscope



2, 1965 D. LITTMANN ETAL STETHOSCOPE 2 Sheets-Sheet 1 Filed June 12, 1962 INVENTOR.

DAVID LITTMANN BY JOHN MGOODNOW g %0%:TTORN1EYS Feb. 2, 1965 D. LITTMANN ETAL 3,168,160

STETHOSCOPE Filed June 12, 1962 2 Sheets-Sheet 2 INVENTORS FIG- -DAVID LITTMANN BY JOHN meooomow ATTOB N EYS United States Patent 3,168,160 STETHOSCOiE David Liitrnann, Belmont, and John M. Goodnow, Greenbush, Mass, assignors to Cardiosonics Medical Instrument Co., Belmont, Mass.

Filed dune 12, 1962, Ser. No. 205,158 19 Claims. II. 181--24) The present invention relates to a stethoscope and more particularly to an improved means for connecting the ear tubes to the sound tube of a stethoscope. This application is a continuation in part of US. patent application Serial Number 140,627 filed September 15, 1961 now abandoned.

Conventionaliy, stethoscopes have a pair of rigid ear tubes interconnected by the arms of a flexible Y member and with the stem of the Y in turn connected to the head of the stethoscope. In such constructions an external spring arrangement spring tensions the ear tubes towards one another so that they may grip the wearers head. Such a construction however has proved to be cumbersome and bulky and in addition is relatively expensive.

Several modifications of this design have been attempted in which the spring member is integrally formed with the Y shaped interconnecting sound tube. Such structures are represented by Morin Patent No. 1,585,407, issued May 18, 1926. These constructions however have not been satisfactory for several reasons.

One ditficulty with such modifications is that the leaf spring arrangement heretofore used cannot withstand continued flexing particularly at the junction of the spring and ear tubes. Such leaf springs contained within the Y shaped sound tube are formed with flanged ends bent into arcuate form to engage the ends of the ear tubes. This junction of the flanged ends and main portion of the spring is quite weak since it is the junction of a curved section and flat section of the spring and therefore provides a natural crease or bending line at which metal fatigue readily takes place. In such structures substantial stress and strain is imparted to this crease line or junction by constant flexing and use which often cause the springs to break at this junction. Attempts to overcome this problem by utilizing cement have not been altogether satisfactory, since such cement does not normally have sufficient strength and will not prevent metal fatigue at this crease line or junction. As a result of these difliculties devices heretofore made of the type referred to are quite susceptible to fatigue fractures at the weakest point of the spring, namely the crease line or junction of the flanges and the main body portion of the spring where bending most naturally takes place.

The present invention is designed to overcome such problems and provides a construction of sufficient strength to better withstand destructive radial torques and longitudinal pulls and thrusts. In stethoscopes made in accordance with the present invention, the ear tubes are secured in selected angular relationship to one another so as to properly engage the wearers ears at all times. In addition, these stethoscopes will not readily break, particularly at the ends of the leaf springs contained within the Y shaped sound tube. Furthermore the present stethoscope can be collapsed to a much more compact structure than can devices made in accordance with earlier known art.

In the present invention there is provided a stethoscope having a pair of rigid ear tubes and a flexible Y shaped sound tube providing two arms and a stem with one ear tube extending outwardly from each of the arms. A leaf spring means comprising at least one leaf spring is contained within the arms of the Y shaped sound tube and extends past the stem into each arm. A securing means positions each end of the leaf spring means to one ear tube. In a preferred form, one leaf spring is employed having opposite ends secured to ends of the ear tubes by crimped solid bushings. In an alternate form of the invention, a pair of leaf springs of the type illustrated in the copending application Serial Number 138,440 filed September 15, 1961, are contained within the arms of a Y shaped sound tube and extend past the stem into each arm. These springs are substantially coextensive with one another and are secured in facing relationship at their ends to the ends of the ear tubes. One leaf spring is rigidly interengaged and the other leaf spring is slidably interengaged at its ends to the ear tubes. Helical coils are wrapped about narrow diameters of the ends of each ear tube and the corresponding ends of the leaf springs to secure the leaf springs in a manner previously set forth to the ends of the ear tubes. The narrow diameter ends of the ear tubes are preferably formed of semicylindrical sections having a diameter less than the main portion of the ear tubes and with opposed longitudinal edges which engage one of the leaf springs in facing relationship.

These and other objects and advantages of the present invention will be more clearly understood when considered in connection with the accompanying drawings in which:

FIG. 1 is a cross sectional elevation of a stethoscope of this invention showing the lower portion or stem of the Y shaped sound tube broken away and without the stethoscope head;

FIG. 2 is an enlarged perspective detail of the interengaged leaf springs and the adjacent end of an ear tube in a device of the type illustrated in FIG. 1;

FIG. 3 is a perspective fragmentary exploded view of the end of an ear tube and the leaf springs secured thereto in a device of the type illustrated in FIG. 1;

FIG. 4 is a fragmentary cross sectional elevation of a preferred embodiment of the stethoscope of this invention showing the lower portion or stem of the \-shaped sound tube broken away and without the stethoscope head;

FIG. 5 is an enlarged side view of a detail of the interengaged leaf spring and the adjacent end of an ear tube of the preferred embodiment of this invention;

FIG. 6 is a cross sectional view taken along line 6-6 of FIG. 5

FIG. 7 is a fragmentary cross sectional detail of a modification of the invention; and

FIG. 8 is a cross section taken along line 88 of FIG. 7.

One form of the invention is illustrated in FIGS. 13 of the drawings showing a pair of stethoscope ear tubes 10 and 11 of conventional shape provided with ear plugs 12 and 13 respectively at their outer ends. The inner ends of the ear tubes 10 and 11 extend into the Y-shaped sound tube 14 having arms 15 and 16 and stem 17, the stem 17 being connected by suitable means to a conven tional stethoscope head (not shown). The Y-shaped sound tube 14 is made preferably of a synthetic resin material such as disclosed in copending application Serial Number 36,641, filed June 16, 1960.

The ends of each of the ear tubes 10 and 11 may be identically formed as illustrated in FIG. 3. As illustrated, the end portion is formed with a reduced diameter. The section of the end portion is milled out partially along its length to form a semicylindrical member having opposed longitudinal edges 19 and 20. The edges 19 and 20 terminate short of the inner end 60 of the reduced end portion 18. A pair of dog ears 21 and 22 project from each of these longitudinal edges 19 and 20 at a distance spaced from the ends of the edges. Preferably these dog ears 21, 22 are spaced closer to the main portion of the ear tube than to the end of the ear tube. The outer end of the reduced portion 18 is beveled as illustrated in FIG. 2 at 26.

The leaf springs 27 and 28 are each formed of parallel strips of spring steel of uniform Width throughout their entire length. Preferably strip 27 which forms the outer strip is slightly wider than the inner strip. In a typical construction the outer strip or spring 27 is wide, While spring 28 is /s" wide. These springs are preferably formed of the best spring steel available and are rolled and formed with rounded edges to avoid damaging the Y shaped sound tube. Outer spring 27 is formed with a pair of notches 30, 31 corresponding in size and shape and adapted to engagedog ears 21, 22. The springs 27 and 28 are secured in facing relation at their ends to the opposed edges 19, 26 of the semicylindrical end section of the ear tubes by a helical coil 35. This helical coil extends from the inner end of the reduced diameter end portion almost but not quite the length of the semicylindrical end portion of the ear tubes, leaving a section 36 (FIG. 2) exposed beyond the end of the coil. The coil extends beyond the end of edges 19, 20 and the springs 2'7, 28 at the inner end of the end portion. This arrangement also normally provides a very small but definite space indicated at 3? between the very end of the ear tubes and the outer surface of the leaf spring 27. These springs 27 and 28 are spaced apart at their center portion indicated at 415 in FIG. 1. This arrangement securely locks the outer leaf spring 27 to the ear tube but allows the leaf spring28 a degree of freedom to slide longitudinally when the ear tubes and 11 are flexed with respect to one another.

The construction described above provides a simple means of indexing the'ear tubes with respect to one another and therefore provides a simple means of securing the ends of the ear tubes in a desired angle one to another, so that they will properly fit the'wearers head. This may be accomplished by a simple milling fixture during the manufacturing process.

In addition to the advantages heretofore set forth, the helical coil securing the springs to the ear tubes compensates for accidental side thrusts or forces and thereby minimizes the likelihood of'a fracture at the junction of the ear tubes and springs when a force is applied in the wrong direction.

The preferred embodiment of this invention is illustrated in FIGS. 4 and 5. A pair of stethoscope ear tubes 45 and 46 of conventional shape are provided with ear plugs 12 and 13 as described above. The inner ends of these ear tubes 45 and 46 extend into a'Y shaped sound tube 14 having arms 15 and 16 and stem 17 as described above. The stem 17 is connected by suitable means to a conventional stethoscope head (not shown).

The ends of each of the ear tubes 45 and 46 may be identically formed as illustrated in FIGS. 5 and 6. The ends of ear tubes 45 and 46 are basically the same as the ends of ear tubes 10 and 11. However, the ends are of the same diameter as the entire length of each ear tube and are formed integrally with each ear tube. The section of the end portion is milled out partially along its length to form a semicylindrical member having opposed longitudinal edges 19 and 20 as shown-in FIG. 3. A pair of dog ears 21 and'22 as shown in FIG. 3, project from each of these longitudinal edges 19 and 20 at a distance spaced from the ends of the edges. Preferably these dog cars 21 and 22 are spaced closer to the main portion of the ear tube than to the end of the tube. The outer end of the tube is beveled as shown at 26.

Preferably a single leaf spring 50 identical to outer spring 27 described above is employed in facing relationship at its ends to opposed edges 19 and 20 of the semicylindrical end of the ear tubes. The spring 50 is secured to the ends by bushings 40 as shown in FIGS. 4 and 5. Each bushing 46 is preferably a solid cylindrical metal member such as stainless steel or brass. Each bushing 40 is preferably firmly secured in place to retain the spring member 56 by crimping the bushing around the assemb ed spring and ear tube ends. Dimples such as 4 shown at 46 and 47 may be employed. Alternatively any crimping means such as corrugated patterns, slots and ridges may be formed to secure the bushing 49 in place.

The bushing extends beyond the edges 19 and 20 and the spring 551 at the inner end of the end portion. At the outer end of the end portion, a portion 36 (FIG. 5) is exposed as in the embodiment of FIGS. 1-3. This arrangement provides a very small but definite space indicated at 39 (FIG. 5) as in the device of FIGS. 1-3. The bushing 40 grips the spring 50 at its outer longitudinal edges as best shown in FIG. 6. Due to the curvature of the cylindrical bushing 21 space is provided between the center portion of the spring end and the inner Wall of the bushing id as seen in FIGS. 6 and 5. Preferably the dog cars 29 and 21 have a height equal to the thickness of the spring 5% and coact with the bushings it to lock the spring to the ear tubes and 46. Preferably, the milled out portion of each ear tube provides an end wall 61 having a height slightly greater than the thickness of spring 59. This feature allows the bushing 46 to grip the spring 59 and also have an inside diameter substantially the same or slightly smaller than the outside diameter of the ear tubes.

Two springs of the type described with reference to FIGS. 13 may be employed in the device of FIGS. 4-6 as illustrated in FIGS. 7 and 8. In this embodiment it is preferred that the end wall 60 have a height slightly greater than the combined thickness of the two springs 50a and 50b.

The device of the preferred embodiment of the invention is extremely strong and secures the spring 59 and ear tube ends together positively preventing disassembly. The use of the solid bushing is particularly advantageous during manufacturing procedures since it is easily mounted by a crimping operation and does not tend to slip off during assembly of the stem 17.

Although specific preferred forms of the present invention have been described, many modifications are possible. For example, in the device of FIGS. 1-3 the springs 27 and 28 may be secured to the ear tubes Without the use of notches or corresponding dog ears. The portion of the ear tubes of the device of FIGS. 1-3 may be of the same diameter as the body portions of the ear tubes.

The invention also contemplates the utilization of notches in the inner spring 23 which may be formed with a greater diameter than the outer spring 27. This latter construction may provide a stronger construction of the tube and spring interengagement because less wall of the tube need be milled out. Similarly, spring 50 may be secured to the ear tubes without the use of notches or corresponding dog cars. In the latter case it is sometimes desirable to crimp a spring 50 along with the bushing 40 to the end of each ear tube. In other embodiments, a single spring may be employed in the device of FIGS. 1-3 or a double spring construction may be employed in the device of FIGS. 4 and 5.

What is claimed is:

1. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y-tube with integral arms and a stem, a pair of elongated leaf springs positioned within said Y-tube arms and prestressed to form U-shaped arcs, and means interengaging each of said leaf springs at their ends to said ear tubes with one spring longitudinally slidable with respect to the other, said means interengaging said leaf springs at each end to said ear tubes including means enclosing portions of said leaf spring ends and said ends of said tubes,said means interengaging such leaf springs at each end to said ear tubes comprising bushings secured about the ends of said springs and the ends of said tubes.

2. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y-tube with integral arms and a stern, a pair of substantially coextensive elongated leaf springs extending longitudinally within said Y-tube arms on either side of said stem and prestressed to form arcs of approximately 180, means interengaging said leaf springs at each end to said ear tubes including means enclosing portions of said leaf spring ends and said ends of said tubes, said tubes each being formed with an end having a semicylindrical wall with opposed edges and with said edges having projecting dog ears formed therein and one of said springs having notches formed therein adjacent its ends with said notches engaging said dog ears and said one spring lying against said opposed edges.

3. A device as set forth in claim 2 wherein the other of said springs is secured with its ends in facing relation and its center portion in spaced relation to said one spring.

4. In a stethoscope construction having a pair of rigid elongated ear tubes with open ends and a flexible Y-tube with integral arms and a stem, leaf spring means comprising fiat leaf springs extending longitudinally within said Y-tube arms on either side of said stem and prestressed to form an arc of approximately 180, means interengaging such leaf springs at each end to said ear tubes including means forming milled out portions at the end of each of said tubes with said milled out portions forming opposed coplanar edges extending at least partially the length of said tube ends from the outer end thereof, said springs lying in adjacent relation with said edges and with enclosing means extending over said milled out portions to secure said springs to said tubes.

5. A construction as set forth in claim 1 wherein said springs are of uniform Width along substantially their entire length.

6. A construction as set forth in claim 1 wherein said bushings are crimped to the ends of said tubes.

7. In a stethoscope construction having a pair of rigid elongated tubes With open ends and a flexible Y-tube with integral arms and a stem, said ear tubes each formed with an end having a semicylindrical wall with opposed longitudinally extending edges, said edges extending partially the length of said tube from the outer end thereof, elongated spring means positioned within said Y- tube arms and prestressed to form an are, said spring means having portions lying in facing relation with said edges and bushings extending over and interengaging said spring means at its ends to said ear tubes at said milled out portions.

8. A construction as set forth in claim 7 wherein said edges are formed with dog ears spaced from the ends thereof, and said spring means includes a spring formed with notches adapted to engage said dog ears.

9. A construction as set forth in claim 8 wherein said elongated spring means comprises a pair of substantially co-extensive elongated leaf springs extending longitudinally within said Y-tube arms with the ends of said springs positioned below said bushings and with one spring adapted to slide relative to the other.

10. A construction as set forth in claim 8 wherein the width of said spring at its ends is no greater than the width of said ear tubes and said bushings are secured by crimp means to said ear tubes with said bushings securing said spring in interengagement with said dog ears.

References Cited by the Examiner UNITED STATES PATENTS 717,898 1/03 McCully 18124 877,317 1/08 Fosgate 181-24 882,700 3/08 Lewis 181-24 1,585,407 5/26 Morin 18124 1,853,951 4/32 Zala 181-24 LEO SMILOW, Primary Examiner. C. W. ROBINSON, Examiner. 

1. IN A STETHOSCOPE CONSTRUCTION HAVING A PAIR OF RIGID ELONGATED EAR TUBES AND A FLEXIBLE Y-TUBE WITH INTEGRAL ARMS AND A STEM, A PAIR OF ELONGATED LEAF SPRINGS POSITIONED WITHIN SAID Y-TUBE ARMS AND PRETRESSED TO FORM U-SHAPED ARC, AND MEANS INTERENGAGING EACH OF SAID LEAF SPRINGS AT THEIR ENDS TO SAID EAR TUBES WITH ONE SPRING LONGITUDINALLY SLIDABLE WITH RESPECT TO THE OTHER, SAID MEANS INTERENGAGING SAID LEAF SPRINGS AT EACH END TO SAID EAR TUBES INCLUDING MEANS ENCLOSING PORTIONS OF SAID LEAF SPRING ENDS AND SAID ENDS OF SAID TUBES, SAID MEANS IN- 